From Task-Based GPU Work Aggregation to Stellar Mergers: Turning Fine-Grained CPU Tasks into Portable GPU Kernels - Dais, Gregor; Diehl, Patrick; Marcello, Dominic; Kheirkhahan, Alireza; Kaiser, Hartmut; Pfluger, Dirk (2022 IEEE/ACM International Workshop on Performance, Portability and Productivity in HPC (P3HPC), Performance, Portability and Productivity in HPC (P3HPC), 2022 IEEE/ACM International Workshop on, P3HPC, 2022)